All references cited in this specification, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features and/or technical background.
Disclosed is a constant velocity transport (CVT) platen having an integrated document illuminator for use in image scanners for recording images from sheets of material, such as paper.
Scanners use different types of light sources to illuminate documents placed on a transparent surface, called a platen. Quality of scanned images depends, among other factors, upon the quality of the luminescence from a document illuminator (comprising a light source) projected onto the document through the platen. Document illuminators are arranged about the platen in various ways, such as underneath the platen, and may include components ranging from one or more lamps, including tungsten and fluorescent lamps, and opposed reflectors. These arrangements may consume relatively large amounts of space in the scanner, and, in some cases, make it difficult to adjust the distance from the document illuminator to the underside of the platen thereby affecting the quality of the scanned image.
A document imaging system associated with a scanner is shown in FIG. 1. As described in U.S. Pat. No. 6,236,470, the system may be employed in either a light lens scanning system or a digital (image input terminal) scanning system in order to illuminate a document for reproduction, display, and/or storage in an electronic memory, magnetic medium, or optical disk. The illumination system of FIG. 1 includes a platen 20 upon which a document 10 is placed. The documents may be dispensed on the platen by a constant velocity transport document feeding roll 15. The glass platen 20 provides for the image positional alignment of the document being fed and scanned by an imager held stationary under the platen at that imaging position while the documents are fed over the top of the platen. As described in U.S. Pat. No. 6,593,995, which along with U.S. Pat. No. 6,236,470 is incorporated herein in its entirety by reference, some scanners have dual mode document imaging systems for either scanning a stationary document with a moving document imager on a large fixed platen or feeding documents past an imaging station on an adjacent smaller platen with the same document imager held stationary.
In FIG. 1, document 10 is illuminated by a light source 50 which provides an active source of light to irradiate the illuminated region of the document. Typically, this source of light is provided by a linear fluorescent lamp (with or without aperture reflecting coatings 60 on the interior lamp surface to form an aperture 65), or by linear tungsten lamps. The light source 50 is situated on one side of an optical center line 40. An imaging system 43, including a lens, causes an image of the portion of the document immediately surrounding this optical centerline 40 to be projected onto a light sensing device 45 comprising a linear array of photo-sensors (full width array sensor), a CCD sensor, or a photoreceptor (not shown). The light reflected from the document about the optical centerline 40 is converted by the light sensing device 45 into electronic signals forming image data which electronically represent the document, and the data may be stored on a recording device such as a memory storage device in a computer.
On the opposite side of the optical center line 40, an opposing reflector 30 is situated. The opposing reflector 30 provides indirect illumination to the document being scanned by redirecting light which would normally not illuminate the document (light leaving the light source in a parallel or substantially parallel path with respect to the platen 20) back to the illuminated region of the document. Reflector 30 reflects scattered light 57 back 35 to the document 10 at an angle opposite from the angle of light being directly 55 emitted by the light source 50. This reflection suppresses shadowing on documents with nonplanar features.
FIG. 2 illustrates an improved document illuminator with substantially smaller dimensions and compact size as set forth in application Ser. No. 10/995,462. The document illuminator system shown in FIG. 2 replaces the lamp/reflector system of FIG. 1. The document illuminator 100 of FIG. 2 comprises a light guide 105 embedded with a small size light source, such as a light emitting diode (LED). Light source region 110 emits light that is directed out of the light guide as rays 120 to illuminate the document 10 on platen 20, as shown in FIG. 2.
It will be appreciated by those skilled in the art that there are usually complications associated with the workings of document illuminators involving trade offs that must be made with regard to system conjugates and lens efficiency in order to accommodate space requirements of the illuminator. The variability of the proximity of the document illuminator on the underside of the platen, and of the thickness of the platen, all contribute to the complexity that can be alleviated by incorporating the light source into the platen itself, as disclosed further below.